


Dirty Little Secret

by snasational



Series: Raffle Prizes [5]
Category: Undertale (Video Game)
Genre: Breeding, Cunnilingus, Dreamtale Sans | Dream (Undertale), Killer Sans (Undertale) - Freeform, Killer Sans/Dreamtale Sans, M/M, Vaginal Sex
Language: English
Status: Completed
Published: 2021-02-17
Updated: 2021-02-17
Packaged: 2021-03-12 09:15:00
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,724
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29507463
Author URL: https://archiveofourown.org/users/snasational/pseuds/snasational
Summary: “God, you’re so dense. If it bothered me I wouldn’t be trying to get into your pants right now.”Dream balks.
Relationships: Sans/Sans (Undertale)
Series: Raffle Prizes [5]
Series URL: https://archiveofourown.org/series/2081718
Comments: 11
Kudos: 148





	Dirty Little Secret

**Author's Note:**

  * For [Menou](https://archiveofourown.org/users/Menou/gifts).



> This took so so long to get out and I’m so sorry about that! I hope you like it despite that!

Dream thinks Killer is interesting. 

Most Sanses like him tend to be. Start off as the prototype and then they diverge into something completely different. At one point, the skeleton before him was a goofy guy that liked puns and science and dumb jokes. And then due to one small change, everything shifts. He’s not Sans anymore, and therefore he goes by a better suited nickname. 

He’s not unique in any sense. Dream has seen hundreds of variations just like him. And yet he’s still a source of fascination for him. One definite reason behind that is because of his brother’s fondness towards the Sans. At first, Dream really didn’t like it. What business did Nightmare have gathering up broken prototypes and befriending them? It invoked a deep sense of jealousy inside of him. 

However, Dream never could hold grudges, even against the people that captured his brother’s heart. It made him sick with envy, of course, but despite that he simply could not hate Killer no matter how hard he tried. So that bitterness morphed into interest, which then morphed into something...else. Dream can’t put a name to it right now, but with the way Killer is looking at him it’s starting to feel a whole lot like lust. 

“I’ve never seen you so far away from my brother.” Dream points out, crossing his arms and leaning against the wall he’s been cornered at. He gives a friendly smile to stave off the nervous arousal that’s washed over him. 

Killer grins and shrugs. “Oh, he’s around.” 

Figures. It’s just Dream’s luck that they always somehow manage to wind up in the same timelines even though there's thousands. It almost feels spitefully intentional, even if that isn’t possible. 

“I see. And you followed me around because?” 

Again, Killer shrugs. “I don’t know. Seemed like fun. Though I ain’t really looking for a fight. Your bro would kill me if I got the final blow on you instead of him.” 

Dream’s expression sours and along with it goes his arousal. How could he forget about Nightmare’s eagerness to kill him? As if abandoning him wasn’t already enough? And since Killer is his underling he surely has the same ambitions. It’s foolish of Dream to be attracted to someone who wants him dead. 

“Aw, don’t make that face. It’s nothin’ personal.” Killer takes a step forward and Dream presses himself closer against the wall. 

“Right. Well if you’re not here to fight then there’s no point in you continuing to interact with me. So, I’d appreciate it if you left me be. I’m a rather busy person, you know.” 

Neither move. Killer cocks his skull. “You wanna know something neat about having so much LV?” 

Dream doesn’t want to know  _ anything  _ about having LV. It’s awful, to waste away the purity of your soul in exchange for power. And to say he isn’t judgemental to those that have gained LV would be a lie. There’s a reason why he sticks to like minded people (although, Ink is like minded for entirely different reasons.)

“No.”

Killer answers anyways. “Well, it heightens your senses! Makes everything better, basically. I can hear better, I can see better, I can  _ smell  _ better.” At the word smell, Killer’s grin takes on a biting edge that has Dream subtly squirming. 

“Okay? Good for you. Anyways, I’ll be-”

The other skeleton starts to chuckle, throwing Dream off. He frowns at the blatant display of mockery. What did Dream say to warrant such a reaction? What a rude, immature Sans. Now, if only his magic would think the same thing about Killer. It has a mind of its own, one that can’t be tamed no matter how hard he tries. It’s certainly led to some... _ unique _ couplings. Like that time prototype Papyrus fucked him so hard his cervix was bruised. 

“You don’t get it, huh?” He begins to stalk closer, inhaling deeply as he closes the distance between the two and cages his arms around Dream’s skull. Dream, like the idiot he is, allows this to happen with bated breath. “I can smell you, Dream. Whenever you get near me I can practically taste how wet your cunt gets. At first I thought it was boss you were getting all horny over. But I had a little inkling, you know? So I followed you around and lo and behold! There goes the smell of your pussy again, how interesting.” 

Mortification fills Dream. Stars, how humiliating! If Killer smelt it, that meant every single one of those Sanses smelled it on him too. Dream has never wanted to curl up and die so badly. 

“I...my apologies if my arousal has brought you discomfort.” Dream meekly apologizes. He stares hard at their feet, refusing to look Killer in the eyes. 

“God, you’re so dense. If it bothered me I wouldn’t be trying to get into your pants right now.” 

Dream balks. Dense?! Indignantly, he looks back up and scowls at Killer. He does his best to ignore how close their faces are and struggles to fight down another wave of lust. Damn it, he’s supposed to be angry right now!

“You can’t call people you want to have sex with  _ dense.”  _

“No?” Killer purrs. Warmth radiated off him like a heater, making Dream feel hot all over. “But I can smell how wet that made you. Come on sweet thing, how about we have some fun? Boss don’t ever have to know. I don’t kiss and tell.” 

Killer is hardly the first person to offer him impromptu sex. And Dream rarely turns around a tumble in the sheets even if he knows he really should. A great example is when a married Dogaressa offered herself to him after an argument with her husband. Unable to turn away such a pretty face, he agreed without any second thoughts. That is, until an axe was thrown at his head. 

Dream almost didn’t make it out of that house alive when Dogamy unexpectedly came home a few hours earlier than planned. It’s not like he  _ wanted  _ to wreck anybody’s home life, but like he said earlier; his dick does all his thinking. It’s been like this ever since he managed to escape that stone prison Nightmare left him in. 

To keep face, he turns his head and huffs. “In your dreams.”

Not one to be discouraged, Killer shoves his hips forward just enough to where Dream can feel his cock grind against his pelvis.

“But look at how hard you got me.” 

Dream really wants to know how Killer fucks. He’s been wanting to know this since he met this damned skeleton, actually. How rough would he be? Would he make Dream cry? He’s always adored a partner who knows how to properly hurt him and something tells him that Killer is the perfect candidate for this. 

“Persistent, aren’t you?” Dream glares weakly. “Does my brother not fuck you enough?” 

Killer snorts. “Not since little Cross came along. That brat has boss’ full attention, and now you have mine. So let’s skip the chit chat, yeah? If you really don’t want to fuck I’ll back off, but your scent is telling me an entirely different story.” 

A hand cups his face, a touch that is surprisingly soft in nature. He’s all for crude sex with someone he hardly knows, but affection and comfort...Dream hasn’t allowed himself that in such a long time. Him and relationships don’t go together. They never last long and they always end on a bad note. The only ex he actively speaks to is Ink, and that really says something, all things considered. 

“Okay. As long as nobody finds out about this.” 

Blue and Ink would give him the world’s longest lecture, that’s for sure. ‘Bad Sanses’ and ‘Star Sanses’ (who came up with that name again? He bets it was Ink) are supposed to be mortal enemies or something. Dream has never gone along with that narrative, really. He thinks it’s kind of dumb, to be honest. But being a part of a group is nice, and Blue makes it worth his while.  _ Nobody  _ gives head better than him. 

“I’m okay with being your dirty little secret.” Killer murmurs into his ear-canal, his voice low and seductive. It sends heat straight to his unformed cunt. 

“I’ve got a hotel room not too far from here.”

-

They don’t even make it to the bed before Killer’s mouth is on his. He eagerly returns the skeletal kisses, relishing in the way magic buzzes between their teeth. It makes him feel intoxicated and he moans unabashedly into Killer’s mouth. Killer responds by lapping at Dream’s teeth with a freshly formed tongue, feverishly begging for entrance. Dream happily grants it and intertwines their magic. 

Killer’s kisses are nice, Dream notes as he urges Killer to the bed. Making it there without breaking contact is a challenge but they somehow make it. It ends with Dream sprawled out beneath Killer. 

“Fuck.” Killer pulls away and curses. He grips onto the sheets next to Dream’s skull tightly, bunching the fabric up in his hands in an attempt to cool down. “God, I want to destroy you. You know what boss put on the no-no list?” 

Dream bites back a groan when Killer thrusts up against his thigh. 

“Messing with you _.  _ You being a whore ain’t really a secret, y’know? And it makes Nightmare  _ so _ mad.” 

This is news to him. Why does Nightmare care? Who Dream has sex with is none of his business. Besides, Dream was under the impression that Nightmare does his best to ignore his existence when they’re not actively fighting. 

“Oh? Nightmare’s perfect little errand boy going against his word? How scandalous.” Dream teases. He loops his arms around Killer and pulls him flush against his ribcage. Killer makes a pleased noise. 

“Never judge a book by its cover.” Killer winks. He dips down for another kiss before releasing the sheets and pulling away completely. “Hey, Dream?” 

“Hm?” He responds, his entire body frozen with anticipation. 

“I’m going to make you my bitch and there’s nothing Nightmare can do about it.” There’s layers of bitterness coating his tone. Without context, Dream doesn’t really understand it. But he’d be damned if those words didn’t send arousal straight to his cunt.

“Okay.” Dream whispers breathlessly. “Prove it then.” 

Killer hooks his phalanges in Dream’s waistband and pulls his pants off in one clean (and impressive) motion before tossing them off into a corner. A soft yellow glow brightens up the room; Dream’s ecto already summoned for Killer’s convenience. 

“I wish I could keep you.” Killer comments as he gets down on his knees in front of the bed. “That way I could use you whenever I wanted. But that’s okay, because I’m going to leave you something to remember me by.” 

“What-? Oh!” 

Killer licks a long stripe up Dream’s cunt, eliciting a mewl from the skeleton. He does this again and again, lavishing Dream’s pussy with light nips and slobbery licks until his thighs are shaking. 

After a while, Dream props himself up on his elbows and stares down at Killer with a desperate expression. 

“Please.” He begs with a trembling voice. “Stop teasing. I’m going to go insane.” 

They make eye contact and Killer gives his clit a little flick. Dream makes a strangled noise and flops back down, spreading his legs wider in hopes that the act of submission will spur Killer on. It seems to work because two fingers slip inside his soaked cunt. 

“Tight.” Killer remarks. He shoves the two of them all the way down to the knuckle. Dream yelps, not expecting the fullness so soon. 

Killer isn’t the first partner to call him tight; it’s something that Dream prides himself on. Killer apparently has intentions on ruining his tightness; the skeleton spreads his fingers  _ wide.  _ It stings. But it isn’t unpleasant, and it’s nothing Dream can’t handle. 

That paired with the way Killer is sucking on his clit makes his orgasm come fast and unexpectedly. He’s so shocked by the sudden and violent waves of pleasure that all he can do is drop his jaw in a silent scream and allow the raw feeling to coarse through him. 

“Woah. You’re a squirter!” Killer says delightedly. Dream responds with something unintelligible, his entire body slack and relaxed. 

He doesn’t even register Killer looming over him again until he’s being kissed firmly. Dream presses back weakly, enjoying the physical affection. He never expected Killer to be a big kisser in bed. He quite likes this newly found knowledge. 

The tip of his cock presses teasingly against his folds. Killer guides himself to Dream’s entrance and thrusts in smoothly. He fits like a glove, filling him up just enough for the pain to be pleasurable. Dream appreciates the girth of him; Killer is a lot thicker than most Sanses. If this is how all of them are, he ought to have sex with more high LV monsters. 

He pulls out until just the tip remains and slams back in roughly, punching the breathe right out of Dream. It continues like this for a while, each thrust more punishing than the last. The brutal pace is exactly what Dream has been craving. For some reason, his partners tend to treat him like a porcelain doll. It’s  _ annoying. _

“I’m going to claim you like nobody else has before.” Killer growls out. “You can fuck whoever you’d like, but the whole fucking multiverse is going to know who  _ claimed  _ you after I’m done.” 

Somewhere in his fucked out brain fear sparks. Those words don’t bode well for Dream. Or Killer. Hey, wait, didn’t they promise to not kiss and tell? There’d be no point in that if Killer is trying to ‘claim’ him.

“What are- ngh, holy shit!” All of his words are lost when Killer’s cock rams against his g-spot. “Motherfucker! Yeah, go on, do whatever you want! Just don’t stop fucking me like that!” 

Killer keeps up the angle and Dream is lost in a world of intense pleasure. There is no other thought in his head except for Killer’s glorious dick. Soon, his second orgasm is brought on. 

While he writhes, Killer slams home one last time and releases heavy ropes of cum inside of him. It twitches and pulses, more and more jizz floods his pussy until it’s overflowing. Jesus, how can a monster outside of heat cum so much? Dream whines at the feeling. 

“You’re taking my cum so well~” Killer pants. “It’s filling you all the way up, Dream. I can see it in your belly.” 

On cue, Killer brings his hand to Dream’s stomach and sends a spark of magic to his soul. He panics for a split second, because if he sends any more magic his soul might take it as an invitation to turn the cum inside of him into fuel for making a baby. But Killer backs off before Dream can react, instead bringing his hand away from his slightly inflated belly to rest on Dream’s hip. 

“Thanks for indulging me.” Killer says, tone happy and relaxed. He slips out of Dream’s ruined cunt with a wet squelch. “I’m going to hop in the shower and then head out. Boss is going to start blowing up my phone pretty soon if I don’t get a move on.” 

Hundreds of one night stands have gone exactly the same way and yet Dream still finds himself disappointed. He doesn’t say anything. He just grunts and throws an arm over his face. Dream is exhausted now, and even if he wants Killer to stay and cuddle he knows it’s for the best if he leaves. 

“Right. Of course.” Dream tries to keep the misery out of his voice. 

When the sound of the bathroom door opening and closing reaches his ears, he rolls over and faces the wall. Is it strange that for a split second, he wishes Killer  _ did _ knock him up? It’d give someone an excuse to stay in his life. It’d allow him to not be lonely anymore. 

God. He’s so fucked in the head. 

-

When he wakes up, there’s a note on his night stand with a number attached to it. 

_ Call me sometime. We can keep being each other’s dirty little secret ;)  _

**Author's Note:**

> 100% inspired by the song Dirty Little Secret by the All-American Rejects -cackles-
> 
> My Twitter is @ snasational


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